1. Field of the Invention
The present invention concerns a filtering or frequency selection device, designed to process microwaves, a device that operates by coupling between at least one dielectric resonator and at least one transmission line such as, for example a microstrip line. This device may be frequency tuned by an electronic control. It is applied, especially, to the making of a tunable oscillator as well to the making of a tunable frequency discriminator which can be used in a device for the frequency stabilization of a tunable oscillator.
For certain uses of a device of this type, for example for radar system equipment, it is necessary to make a device which has frequency agility, which can be tuned to a wide freqency band and, in addition, has high tuning speed. To be fitted to an airborne or homing radar system, a device of this type must also be as small and as light as possible.
2. Description of the Prior Art
Devices of this type are known. One such known device has:
two microstrip lines;
a dielectric resonator located on the substrate constituting the dielectric of the said lines (hereinafter designated simply as the substrate) and close enough to these lines to be coupled to each of them:
a varactor, i.e. a capacitor capable of variation according to the voltage applied to its terminals, mounted on one of the lines.
A signal injected into the device is filtered, and the obtained center frequency of the filtering device can be made to vary by controlling the voltage applied to the varactor.
However, this known device is tunable only on a band which is small as compared, for example, with a filtering device having a YIG resonator.